K&N Air Filter Change

[Future]

If you change a stock air filter for a K&N do you have to rejet the carb. That is what the guy at the MSF course told me. I have a 05 Ninja 250R and am just looking for a little more power until I can pay this off and get something bigger.

[QKENUF4U]

leave it alone and ride the $HIT out of it. learn to ride that bike to its limits and you wont have the need for more power anytime soon. theres not really anything thats gonna give you MORE power per say on your 250. (gutless wonder)

[Future]

If I did change it would I have to rejet the carb?

[oldcoldankles]

I didn't have to rejet mine - it ran a little bit leaner so I got better gas mileage but still ran fine.

[NY_Guy]

If you change a stock air filter for a K&N do you have to rejet the carb. That is what the guy at the MSF course told me. I have a 05 Ninja 250R and am just looking for a little more power until I can pay this off and get something bigger.

You won't know definitively until you change the air box and check the plugs-- if they're white, it's running too lean and you must rejet the carb (or end-up frying the valves). But don't ride it too far (3-5 miles is plenty) with full throttle spectrum.